A substantial number of older adults appear neither cognitively intact nor demented, but have minimal impairments that are intermediate between these two states. The term Cognitive Impairment, No Dementia (CIND) has been used to describe this broad group, regardless of etiology. Subgroups of CIND have been described using several terms, including Mild Cognitive Impairment (MCI) often used to describe a prodromal or risk state for dementing disorders. While clinically useful, these terms, concepts, and criteria are less reliable in the broader community setting, where they seem to identify unstable and heterogeneous categories. Yet, the importance of identifying those with true incipient dementing disorders cannot be overstated, given the growing likelihood of secondary prevention/ early intervention strategies in those most likely to progress to dementia. This revised application is for a new epidemiological project to be carried out near Pittsburgh (PA). Specifically, we will describe the distribution of CIND/ MCI and related entities, their associated features, their outcomes over time, and the predictors of these outcomes. An age-stratified random community sample of approximately 2,100 will be recruited and screened using cognitive, functional, and other health-related measures, to identify the non-demented who are cognitively impaired. Among them, we will identify subgroups meeting operational criteria for MCI of amnestic and other varieties. Participants will be further classified according to multiple, potentially overlapping, schema which are in currently use by different groups. Subgroups will be also characterized with regard to demographic, clinical, and biological variables which may predict outcomes and/or have diagnostic significance. Annual follow-up assessments will track changes in cognitive and functional ability and identify transitions to clinical states including Alzheimer's disease and other dementing disorders. Analysis of these prospectively gathered data will allow subgroups to be defined according to outcome, and thus permit the empirical refinement of clinical and research criteria for various forms of mild cognitive impairment.